Determination of As and Sb in steels by electrothermal atomic absorption spectrometry after reduction, complexation and sorption on activated carbon

A method for the preconcentration and separation of As and Sb in steel samp le solutions is proposed. The analytes are reduced to their trivalent oxida tion states with a mixture of ascorbic acid and potassium iodide and comple xed by the ammonium salt of dithiophosphoric acid O,O-diethyl ester. The co mplexes are sorbed onto carbon. After desorption in a small volume of nitri c acid solution, As and Sb are determined by electrothermal atomic absorpti on spectrometry. Iron(III) is also reduced to Fe(II), which is not complexe d and is about 99.9% eliminated by the preconcentration procedure. Enrichme nt factors of 5 and 10 were obtained for As and Sb, respectively. The metho d was applied to the analysis of four certified steel samples, after acid d issolution in a microwave system and good agreement was obtained with the c ertified values.